Actual compression in pounds per square inch vs the compression ratio

[Chuckcruzin1986]

Hello,
I am increasing the compression ratio on my M20 (2.7 with 885 head) and find it difficult to measure the combustion chamber and piston displacement (volume above the face of the block). I am taking a chance and milling .050" of the head plus turning stock of the top of the pistons so to clear the combustion chamber.

So, I was wondering if someone could give me the data of their engine's compression and what compression ratio they have. 2.5 or 2.7 engine.

325 super eta 8.5 - 1 ________

325i 8.8 - 1 _________

325i with 9.5 - 1 __________

325i with 10 - 1 ____________

325i with 11 - 1 _______________

I am guessing that when my engine is done I will check compression and get and idea what I actually ended up with :)

Obviously, I hope to hit mine somewhere near my goal of 10 - 1

Thanks, Chuck

[whodwho]

Not really a good method to calculate it as there are many variables the cam being a large one.

You could CC the head and then CC the chamber thru the plug hole with the head on and piston greased.

FWIW, I have a 325 with a SETA head and cam skimmed 20 thou and have 200psi on a compression test. I believe it to be high because of the smaller duration cam (running a SC).